When a water tap cannot be turned manually by reason of the physical infirmity or handicap of the user, or perhaps by reason of attempts to avoid transfer of bacteria such as in operating theatres, veterinary establishments and the like, special taps are often installed. One known tap has a lever for operation by the elbow instead of a cross head for operation by the fingers. Such taps are not easily operable by armless persons, persons who cannot bear skin pressure and persons with a poor sense of touch such as occurs in paralysis. In situations where showers are controlled by screw taps or a mixer tap provided with a temperature dial, often no special provision is made for the prevention of scalding which could occur in the event of an unexpected reduction in cold water pressure.